The invention relates to a vehicle having an N-phase electric machine, a first on-board electric sub-system and a second on-board electric sub-system, wherein the electric machine comprises a rotor and a stator system, the first on-board electric sub-system comprises an inverter, the stator system is linked to the inverter and the electric machine can be operated using an inverter controller according to the principle of a field-oriented control system.
Components that are electric energy consumers are usually supplied with a rated voltage of 14 volts in a vehicle. A secondary 12 volt energy storage system, which assumes the function of an energy source or the function of an energy sink of any on-board electric system and a 14 volt generator are designed to supply an electric power of usually 1.5-3 kW in the vehicle.
If multiple consumers having an increased power demand are integrated into the on-board electric system of the vehicle, then the on-board electric system may have two or more on-board electric sub-systems. A DC chopper converter then transfers electric power between the two on-board electric sub-systems. The electric machine, which can also be operated as an engine in a vehicle having an electrified drive train, functions as an electric energy source or as an energy sink in the vehicle, in addition to at least one energy storage system per on-board electric sub-system. Such an on-board electric system topology is described in the publication DE 102 44 229 A1, for example.
One object of the invention is to describe an improved vehicle having an N-phase electric machine, a first on-board electric sub-system and a second on-board electric sub-system, wherein the electric machine comprises a rotor and a stator system, the first on-board electric sub-system comprises an inverter, the stator system is linked to the inverter and the electric machine can be operated with an inverter controller according to the principle of a field-oriented control system.
According to one embodiment of the invention, a control unit is linked to the electric machine, the inverter can be controlled by the control device and the control unit controls the inverter in the form of a phased activation method.
This means that the stator system of the electric machine is linked to the inverter and the electric machine can be operated with a current controller according to the principle of field-operated regulations, wherein a phased activation method which utilizes both the leakage inductance and the main inductance of the machine for smoothing the neutral point current is used.
In other words, this is a vehicle having an N-phase electric machine, a first on-board electric sub-system and at least one second on-board electric sub-system, wherein the electric machine comprises a rotor and a stator system, and the first on-board electric sub-system comprises an inverter for converting a DC voltage into an AC voltage. This may be a bridge circuit or some other topology such as a multi-level converter. At the input of this inverter, there is an intermediate circuit capacitor for smoothing the input voltage in the case of an applied voltage or an intermediate circuit choke for smoothing the input current in the case of an impressed current.
According to a preferred variant of the invention, it is advantageous if the stator system is embodied in a delta connection, if the neutral point can be connected to the second on-board electric sub-system directly or via a neutral point switch, if the inverter controller comprises a current controller and a neutral point controller, if the current controller regulates phase currents of the stator system and if the neutral point controller regulates a neutral point current.
It is expedient if the vehicle comprises measurement means for measuring a number of at least N−1 phase currents and the neutral point current, or if the vehicle has measurement means for measuring a number of at least N-phase currents or if the vehicle has measurement means for measuring an intermediate circuit current, wherein the measured intermediate circuit current enables at least one indirect determination of the N-phase currents of the machine on the basis of the voltage null pointers and the control unit comprises the inverter controller.
According to a preferred embodiment, the phased activation method smooths the neutral point current, wherein the neutral point current is smoothed by a leakage inductance and by a main inductance of the machine and a phased activation of the individual phases by a respective pulse pattern, and the pulse patterns are advantageously shifted by an angle of 360°/N.
According to another variant of the invention, the phased activation method serves to smooth the neutral point current by minimizing current ripples of the neutral point current, and the phase shift acts without torque in the rotor in regulation of the neutral point current, averaged over one revolution of the machine.
This means that, when averaged over one revolution of the machine, no additional torque is generated in the rotor.
Special advantages are obtained when the phased activation method can be used for an increased adjustment frequency in pulse pattern generation to reduce a switching frequency of the inverter to improve efficiency, or at a predetermined switching frequency to expand the operating range of a pulse width-modulated (PWM) regulation, which is limited by the rotational speed of the machine, in the direction of a higher rotational speed of the machine, and the neutral point controller supplies a control value for the activation method.
Thus, at a predetermined switching frequency, the PWM operating range, which is limited by the pole-changing frequency of the machine and thus by the rotational speed of the machine, can be shifted toward higher rotational speeds.
Another expedient embodiment of the invention is obtained when the measurement means are measuring N currents (Iu, Iv, Iw) of the electric machine, and the control unit transforms the measured currents (Iu, Iv, Iw) via an extended Clarke and Park transform into a field-oriented current indicator (Id, Iq, I0) with a flux-generating component (Id), with a torque-forming component (Iq) and with a current zero component (I0), wherein the neutral point current (Ineutral) is three times as much as the current zero component.
In addition, it is advantageous if the inverter controller has the flux-generating component as a regulating variable, if the inverter controller has the torque-forming component as regulating variable, if the inverter controller has the current zero component as a regulating variable, if the inverter controller has a first setpoint current variable (I*d) for the flux-generating component as a setpoint variable, if the inverter controller has a second setpoint current variable (I*q) for the torque-forming component as a setpoint variable, if the inverter controller has a neutral point setpoint current (I*neutral) as a setpoint variable, if the inverter controller outputs a first stator control voltage (U*d) as a control variable, if the inverter controller outputs a second stator control voltage (U*q) as a manipulated variable and if the inverter controller outputs a third stator control voltage (U*0) as a manipulated variable.
This is expediently supplemented by the fact that the N-phase electric machine is designed as a three-phase electric machine, the inverter comprises six inverter circuits (HS1, HS2, HS3, LS1, LS2, LS3), the six inverter circuits are arranged in three half bridges for the three phases of the stator system, the first stator control voltage, the second stator control voltage and the third stator control voltage can be transformed by an extended inverse Clarke and Park transform into phase voltages (Ua, Ub, Uc) of the stator system, and the inverter switches the phase voltage for each of the phases in a shift cycle according to the principle of pulse width modulation.
According to another variant of the invention, the electric machine transfers electric power from the first on-board electric sub-system to the second on-board electric sub-system when the neutral point switch closed and when a neutral point current (Ineutral) has a current direction from the neutral point to the second on-board electric sub-system and acts as a step-down converter.
In the case of a direct connection or a closed neutral point switch, the electric machine transfers electric power from the second on-board electric sub-system to the first on-board electric sub-system in the case of a neutral point current (Ineutral) having a current direction from the second on-board electric sub-system to the neutral point and acts as an step-up converter.
Furthermore, by stipulating the neutral point setpoint current and adjusting the neutral point control voltage, a neutral point current (Ineutral) can be adjusted and the electric machine acts as a bidirectional power controller when the neutral point switch is closed.
Preferred exemplary embodiments of the invention are described below on the basis of the accompanying drawings. These yield additional details, preferred embodiments and refinements of the invention. In detail they show schematically:
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.